July 09, 2007

I'll be damned! Douglas Adams nailed it! The mystical number in the Hitchhiker's Guide to the Galaxy, 42, is a key number in predicting the actual weight of the Universe.

As you may remember, the Answer to The Ultimate Question Of Life, the Universe and Everything is simply "42," the numeric produced using the hypercomputer, Deep Thought, after a very long computation time (7.5 million years).

But Deep Thought's abilities came up short when asked to provide the
Ultimate Question to match the answer of 42. Thereafter, the answer
given by Deep Thought prompts Arthur Dent and the Hitchhikers to
embark on a quest to discover the Question to which this is the Answer.

Once again, art anticipates science: after pondering the weighty
question of the mass of the Milky Way galaxy, astronomers have come up
with an answer: 42! Our galaxy weighs three times 10 to the power of 42
kilograms - a number written as 3 followed by 42 zeroes.

It seems esoteric but knowing the weight of the galaxy - the amount
of matter it contains - is key to solving the nature of so-called dark
matter. Unlike the "ordinary matter" of stars and planets, scientists
have only hunches about the nature of the invisible material that,
along with "dark energy", they estimate makes up 90-99 per cent of the
universe.

What is it? How is it distributed across the
universe? Does it really even exist? "That's worth knowing," said
Professor Freeman,an astrophysicist with Mount Stromlo Observatory and
the Australian National University's Research School of Astronomy and
Astrophysics in Canberra said in an interview with The Australian. So along with colleagues in Australia, Europe, the US and Britain, he decided to "weigh" a galaxy.

The problem is there's no good way to quantify all the dark matter in
distant galaxies, thus making it difficult to total all the matter,
dark and ordinary. So Freeman and his colleagues focused on our home
galaxy, the Milky Way, an average sized spiral galaxy, containing a few
hundred billion stars (keep in mind that there are some 100 billion
galaxies in the observable universe, each containing more or less the
same number of stars).

It has been determined that there is a roughly spherical halo of dark
material stretching out to distances of perhaps 10 times as far from
the center of the galaxy as we are.

"Because we're inside our galaxy, we can get a more reliable measure
of the dark matter content than we can for galaxies outside," he said.

To
do so, the group first estimated the "escape velocity" of the galaxy -
the speed stars passing near the sun needed to attain in order to
escape its gravitational pull. It did so using the line-of-sight, or
radial, velocity of stars crossing the central rotating disc of the
galaxy.

The data was collected by the 1.2m Schmidt Telescope of
the Anglo-Australian Observatory at Siding Spring, NSW. The escape
velocity, calculated at between 544km/sec and 608km/sec, allowed the
team to calculate the Milky Way's mass and weight, as well as the
amount of dark matter: 94 per cent.

Wow...that's cool! We think Professor Freeman and team should be awarded the "Galactic Institute's Prize for Extreme Cleverness."

Roughly speaking, the amount of mass observable Does only have 40 zeros. It's the UNobservable mass that adds the 2 more zeros. While these guys round up and down like we all do, they understand the difference in going for a 3 mile jog and a 300 mile jog...

I hate to be picky, but the galaxy has no weight. Weight is a measure of how much the gravity of a planet is pulling on an object. Example, astronauts weigh less on the moon than the do on the Earth. The measure your looking for is Mass. The mass of the Milky Way is 10 to the power of 42.

If you take a gravitational source, add up the relative weights of an object from all positions on a sphere equidistant from the center, positive and negative, the total is 0. Add all gravitational sources, the total is 0.

Therefore the galaxy weighs 0, with a mass of 3 X 10^42, if you agree with deep thought and the people that came up with it, which I don't because I'm not ready to stop my program...